There exists a variety of apparatus for the mixing and blending of liquids and viscous materials. These include mixers or blenders that have rotating impellers as does the instant invention. Examples of such mixers are shown in U.S. Pat. Nos. 1,304,349; 1,582,518; 2,159,856; 2,918,264; 3,273,865; and 3,404,870. While some of these mixers operate satisfactorily on certain materials, a problem remains particularly in the food industry in mixing powders with liquids as in the case of powdered milkshake materials, or in mixing of viscous food materials as exemplified by the pureeing of beans. The problem involves obtaining the proper rotational flow in combination with a suitable vortex for drawing materials such as dry powder into the liquid and the mixing of materials drawn by the vortex into the liquid phase in the mixer. According to this invention, the rotational flow is interrupted by baffles to convert the circumferential laminar flow to turbulent flow to promote mixing in the circumferential area of the mixer.
It has been found according to this invention that good results in mixing powdered materials into liquids such as milkshake materials into milk, or in mixing vegetable materials such as beans to obtain a puree, can be obtained in an impeller type mixer which operates together with a novel baffle arrangement.
According to the invention, there is provided an axial impeller mounted for rotation in a container. Further provided are removable stationary baffle means spaced radially outwardly of said impeller blade with at least a portion thereof extending upwardly from the plane of rotation of the impeller. The baffle has at least two axially spaced aperture means located intermediate the inner and outer edges of the baffle at a location in the upwardly extended portion of the baffle means to permit a portion of the mixable material to which rotational motion has been imparted to flow through the baffle. In a preferred form of the invention, the first aperture is at a position approximately level with the upper level of the mixable material in the container and the second one of the apertures is located at least about 40% of the axial distance from the plane of said impeller to the location of the first aperture. By spacing the apertures in this manner, it has been found that sufficient laminar flow is maintained through the baffles to maintain the vortex necessary to draw the solid materials to the area surrounding the impeller while at the same time sufficient turbulent flow is caused by the baffles to provide the mixing action. The laminar flow through the apertures also picks up the mixed material that has been agitated by being impeded against the baffles to carry it on around the edges of the container to the next baffle impediment.
As will be hereinafter described, the mixer of the current invention provides excellent results in mixing food materials not heretofor obtained by prior art mixers. In the case of powdered materials to be mixed into a liquid, the powdered phase must be intimately contacted with the liquid to achieve a fully mixed food product. This is also true in the case of pureeing foods such as beans wherein the skins or particles of varying density will form a separate phase that must be intimately mixed with the bean pulp to form a smooth pureed food.
It was an object of this invention to provide a mixer and blender for mixing powders in liquids and for mixing other food stuffs wherein the parts could be easily cleaned and removed from mixing containers.
A further object of this invention was to provide a mixer which could economically and efficiently mix various materials.
A further object of this invention was the provisions of a mixer baffle which could be inserted into an existing mixer container to obtain optimum mixing efficiency.
These and other objects of the invention were satisfied by the novel mixer and blender of this invention which is described herein.